In thermal separation processes, columns which have trays, for example sieve trays, valve trays, dual-flow trays, etc., as internals having separation activity are frequently used. The trays must be detachably fastened to the inner wall of the column, as a rule via a support ring. For this purpose, it is usual to screw the trays to the support ring, for example as described in EP-A 0 856 343. However, it is also possible to carry out the detachable connection of the tray to the support ring by means of clamps.
Suitable thermal separation processes are in particular the rectification and absorption processes. Here, it is frequently necessary to treat thermally unstable substances which tend to polymerize under the process conditions. Particularly critical here are, inter alia, the connecting elements between trays and support rings, i.e. the screws or clamps described above.
EP-A 0 856 343 discloses a retaining apparatus for column trays, an orifice through which liquid can flow away being provided in at least a part of the retaining apparatus.